The present invention relates generally to methods and systems for wireless communications and, more particularly, to protocols used in wireless communications to send and receive packet data.
Packet switched communication networks evolved from the need to conserve data communication resources. Since data is sent in discrete packets, rather than as a continuous transmission, gaps in communication on one connection can be efficiently utilized by providing packets from other connections to fill those gaps. Since there is no direct connection between terminals in a packet switching environment, the link is called a virtual connection. Rather than being readily identified by its association with a direct, physical channel, a connection on a packet switched network using a virtual channel is instead determined by a plurality of identifiers. These identifiers, and other information needed to provide smoothly flowing communications in packet switched networks, are provided by protocols which define the rules of communicating on a packet switched network. These rules are also needed so that system programmers and developers have a common baseline from which to design compatible systems.
There are many different protocols for communicating over networks in general. Some protocols, such as the AT protocol commonly used in computer modems, were initially designed for wire-bound networks and later expanded for use in wireless networks. Wire-bound networks, however, are relatively high speed systems as compared with wireless networks since it takes much longer to propagate a packet in a wireless environment. Thus, wire-bound protocols are not designed to effectively handle the idiosyncracies of wireless systems, e.g., propagation delays, transmission disturbances, etc.
Other protocols are provided in communication network adaptor cards which allow computers to communicate over, for example, wide area or local area networks. Examples of this type of protocol include Ethernet, TCP/IP, NetWare, etc. Much like the AT protocol, however, these protocols were designed with high speeds, e.g., 10 Mbits/s, in mind.
Asynchronous transfer mode (ATM) is a more recent development in the communication protocol arena which can be used to transfer data with different requirements on a broadband ISDN network. Like the other protocols, however, ATM is defined only for high speed connections.
A network known as the Mobitex network has its own protocol, the Mobitex Asynchronous Communication (MASC), which is defined for a serial interface between a computer and a modem. This protocol, however, is complex and difficult to use. Moreover, MASC was developed a number of years ago without considering the possibility of wireless communication and has several limitations in this regard. For example, an eight bit data byte is coded as two data bytes according to MASC so that each byte can be sent as seven data bits with one bit parity.
Over the years, MASC has evolved and new commands have been added. Unfortunately, these additions to MASC have not always been consistent and, thus, there is no one algorithm or set of commands which is generic. Instead, each command is unique which creates many problems for those using the Mobitex system. Delimiters exemplify the inconsistencies of the MASC protocol. MASC uses both "," and "/" symbols as delimiters. Even the usage is inconsistent, as MASC sometimes uses delimiters even when the parameters being communicated have fixed lengths.